Accumulation rates during 1311-2011 CE in North Central Greenland derived from air-borne radar data

Radar-detected internal layering contains information on past accumulation rates and patterns. In this study, we assume that the radar layers are isochrones, and use the layer stratigraphy in combination with ice-core measurements and numerical methods to retrieve accumulation information for the northern part of central Greenland. Measurements of the dielectric properties of an ice core from the NEEM (North Greenland Eemian Ice Drilling) site, allow for correlation of the radar layers with volcanic horizons to obtain an accurate age of the layers. We obtain 100 a averaged accumulation patterns for the period 1311-2011 for a 300 by 350 km area encompassing the two ice-core sites: NEEM and NGRIP (North Greenland Ice Core Project). Our results show a clear trend of high accumulation rates west of the ice divide and low accumulation rates east of the ice divide. At the NEEM site, this accumulation pattern persists throughout our study period with only minor temporal variations in the accumulation rate. In contrast, the accumulation rate shows more pronounced temporal variations (based on our centennial averages) from 170 km south of the NEEM site to the NGRIP site. We attribute this variation to shifts in the location of the high?low accumulation boundary away from the ice divide.

雷达探测得到的冰内层理蕴含了过去积雪积累速率与分布模式的相关信息。本研究假设雷达探测得到的冰层层理为等时线，结合冰芯测量数据与数值方法，提取格陵兰中部北部区域的积雪积累信息。通过对取自NEEM（North Greenland Eemian Ice Drilling，北格陵兰埃姆间冰期冰芯钻探计划）站点的冰芯介电特性进行测量，可将雷达层理与火山层位进行关联，进而确定冰层层位的精确年代。本研究针对涵盖NEEM与NGRIP（North Greenland Ice Core Project，北格陵兰冰芯计划）两个冰芯站点的300 km×350 km区域，获取了1311年至2011年期间的百年平均积雪积累分布模式。研究结果呈现出明确的空间分布趋势：冰盖分水岭以西积雪积累速率较高，以东则较低。在NEEM站点，该积雪积累模式在整个研究时段内均保持稳定，仅存在微小的时间尺度波动。与之相反，在NEEM站点以南170千米至NGRIP站点的区域内，基于百年平均的积雪积累速率呈现出更为显著的时间变化特征。我们将该变化归因于高低积雪积累边界的位置偏移，该边界偏离了冰盖分水岭。